Optical-SEM Inspection Alignment for High-Resolution Defect Verification
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Solution Overview
Problem
High resolution inspection of advanced nodes faces challenges with optical-based sample coordinate alignment and calibration, leading to poor precision and time-consuming defect inspection due to limited optical image quality and resolution.
Innovation Solution
An inspection apparatus integrating an optical imaging system and a scanning electron microscope (SEM) system within a vacuum chamber, utilizing high-resolution SEM images for real-time alignment and calibration, and modifying optical conditions based on SEM references to enhance precision and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical imaging system is used for sample coordinate alignment and defect inspection, then inspection speed is improved, but measurement precision and position accuracy deteriorate due to resolution limitations
Solution Approach 1:
The patent combines optical imaging system and SEM system into a single integrated inspection apparatus. The optical system performs rapid defect inspection while the SEM system provides high-precision position alignment and calibration. Both systems share a common sample stage and coordinate system, allowing the fast optical inspection to benefit from the precise SEM-based positioning without sacrificing speed.
2Measurement precision
If SEM system is used for defect inspection, then measurement precision is improved, but inspection time increases significantly
Solution Approach 1:
The inspection process is segmented into two stages: first, the optical imaging system performs rapid screening to identify potential defect regions; second, the SEM system is applied only to those specific regions for precise verification. This segmentation allows the high-precision SEM to be used minimally, reducing overall inspection time while maintaining high defect detection precision.
Solution Approach 2:
Instead of applying SEM to the entire sample, the system applies SEM only partially to regions of interest identified by the optical system. This partial action approach achieves sufficient defect detection precision without the excessive time cost of full-sample SEM inspection.
3Ease of operation
If optical imaging system operates in air environment, then operation ease is improved, but image quality deteriorates due to light scattering and absorption
Solution Approach 1:
The patent places both the optical imaging system and SEM system within a vacuum chamber. The vacuum environment eliminates light scattering and absorption by air molecules, significantly improving optical image quality and reliability. The vacuum environment is compatible with both optical and SEM operations, allowing high-quality inspection without compromising system accessibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The integrated system reduces alignment errors and inspection time, improves precision, and increases efficiency by using SEM images for real-time calibration and defect verification, minimizing false rates and optimizing optical imaging system parameters.
Implementation Method 1
The optical imaging system includes a light source, an illuminator, an imaging optical, and an image sensor. The light source is configured to emit a light beam.
Implementation Method 2
The SEM system includes an electron source, a column, a high voltage system, scan driver, a lens driver, and an image channel system.
Data Source
AI summary
A inspection apparatus includes a sample stage, an optical imaging system, and a scanning electron microscope (SEM) system. The sample stage is configured to bear a sample. The optical imaging system is configured to obtain a first image from the sample stage. The SEM system is configured to obtain a second image from the sample stage. The inspection apparatus is placed in a vacuum chamber.